Thin film deposition of metal oxides in resistance switching devices: electrode material dependence of resistance switch
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NANO EXPRESS
Open Access
Thin film deposition of metal oxides in resistance switching devices: electrode material dependence of resistance switching in manganite films Toshihiro Nakamura*, Kohei Homma and Kunihide Tachibana
Abstract The electric-pulse-induced resistance switching in layered structures composed of polycrystalline Pr1−xCaxMnO3 (PCMO) sandwiched between Pt bottom electrode and top electrodes of various metals (metal/PCMO/Pt) was studied by direct current current–voltage (I-V) measurements and alternating current impedance spectroscopy. The I-V characteristics showed nonlinear, asymmetric, and hysteretic behavior in PCMO-based devices with top electrode of Al, Ni, and Ag, while no hysteretic behavior was observed in Au/PCMO/Pt devices. The PCMO-based devices with hysteretic I-V curves exhibited an electric-pulse-induced resistance switching between high and low resistance states. Impedance spectroscopy was employed to study the origin of the resistance switching. From comparison of the impedance spectra between the high and low resistance states, the resistance switching in the PCMO-based devices was mainly due to the resistance change in the interface between the film and the electrode. The electronic properties of the devices showed stronger correlation with the oxidation Gibbs free energy than with the work function of the electrode metal, which suggests that the interface impedance is due to an interfacial oxide layer of the electrode metal. The interface component observed by impedance spectroscopy in the Al/ PCMO/Pt device might be due to Al oxide layer formed by oxidation of Al top electrode. It is considered that the interfacial oxide layer plays a dominant role in the bipolar resistance switching in manganite film-based devices. Keywords: Resistance switching, ReRAM, Manganite, PCMO, Impedance spectroscopy
Background Recently, a large resistance change by the application of an electric pulse was observed at room temperature in metal oxides such as Pr1−xCaxMnO3 (PCMO) [1-31]. This effect provides a possibility of a next-generation nonvolatile memory, called resistance random access memory (ReRAM). ReRAM is highly expected to replace conventional flash memory due to its low power consumption, small bit cell size, and fast switching speed. The underlying mechanism of the resistance switching behavior is still poorly understood, although there have been various proposed models of the resistance switching mechanism such as formation and rupture of conductive filament paths [3,4], field-induced electrochemical migration such as oxygen vacancy creation/diffusion [5,6], alteration of the width and/or height of a Schottky-like barrier by trapped * Correspondence: [email protected] Department of Electronic Science and Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
charge carriers in the interface states [7], trap-controlled space-charge-limited current [8-12], injecting electrons into and extracting electrons from the interface [13], and oxidation/
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